NEW YORK (CBSNewYork) — Dead fish have been coming up to the surface of the Prospect Park Lake in Brooklyn.

A 1010 WINS listener, who asked to remain anonymous, said she noticed “hundreds” of dead fish in the lake Thursday morning. She took a video of what she saw and sent it to the station.

The Prospect Park Alliance said it is investigating.

“The Prospect Park Lake is experiencing a sudden decline in its fish population. We believe this is due to the extreme heat and lack of rain and wind over the past several weeks. This can cause a severe drop in oxygen levels that endanger fish,” the group said in a statement.

The alliance said it was first alerted to the issue late Tuesday.

“We do not have a formal count yet on the number of fish, but it is in the hundreds,” the alliance said.

It is working with the New York State Department of Environmental Conservation to confirm the cause of the issue.